The recent performance improvements in organic-inorganic perovskite solar cells (PSCs) was brought by incorporating formamidinium (FA+) cation into their crystal structure. However, their imbalanced charge-transport characteristics and inferior light-absorption capability, with respect to methylammonium lead halide perovskite (MAPbX3, X=I, Br, and Cl), have hindered broad application of FA-based perovskites in optoelectronic applications with a planar architecture. Thus, there remains a need for perovskite films and devices having improved physical property and/or performance metrics, as well as a need for improved methods for manufacturing such films and devices.